1. Field of the Invention
The present invention relates to a contact unit which is disposed between a first electrical part and a second electrical part and in which the first electrical part and the second electrical part are connected electrically through a plurality of contacts.
2. Prior Art of the Invention
Conventionally, in some type of a contact unit for testing electrical parts, a plurality of plates into which a plurality of contacts are inserted are provided and a plurality of through holes into which a plurality of the contacts are inserted are formed in each plate, the contact being extended/contracted within the through hole so as to achieve electrical contact between the electrical parts through the contact.
As an invention concerning the technology of such a contact disposing structure, an invention as described in Patent Document 1 (Japanese Patent Application Laid-Open Publication No. 2003-307542) has been known. The patent document 1 describes with reference to its FIGS. 1-13, “a socket for an electrical part which is disposed on a wiring board and has a socket body for accommodating the electrical part, the wiring board and the electrical part being electrically connected through a plurality of contacts disposed on the socket body, wherein an accommodating member on which the electrical part is mounted is provided on the top of the socket body while the wiring board is provided on the lower side of the socket body and a plurality of plates are stacked between the accommodating member and the wiring board without any gap, the plurality of the plates including upper plates disposed at the uppermost position, a lower plate disposed at the lowermost position and an intermediate plate disposed between the upper plate and the lower plate. Further the same document describes “the contact comprising a terminal side contact member which makes contact with a terminal, a base plate side contact member which makes contact with the wiring board, and a spring member provided between the terminal side contact member and the base plate side contact member, the terminal side contact member having a first rod-like portion which makes contact with the terminal and a first flange portion which is provided halfway of the first rod-like portion and makes contact with an upper end of the spring member, the base plate side contact member comprising a second rod-like portion which makes contact with the substrate and a second flange portion which is provided halfway of the second rod-like portion and makes contact with a bottom end of the spring member, the first flange portion and the second flange portion being disposed within an intermediate through hole formed in the intermediate plate”.
In case of manufacturing the contact disposing structure having stacked plates described in the patent document 1, a plurality of through holes are formed in each plate. Upon production of multiple kinds of products in each small quantity, manufacturing by cutting requires less manufacturing cost and shorter manufacturing time than manufacturing with a mold.
However, if the through holes are formed by cutting, more time and more cost may be required than a case of molding in order to obtain a higher accuracy and there is a fear that any mounting misalignment may occur between plates to be stacked. Therefore, the through hole needs to be made larger than required, which is a problem to be solved.
On the other hand, if the contacts are disposed to a socket for an electrical part at a small pitch, there is a limitation in reduction of the thickness of a partition wall portion which sets the through holes apart from each other at an interval.